CD8+ T cells are involved in immune responses to antigens. Reducing their number and/or function can ameliorate undesired immune responses. Doing so, however, with conventional immunosuppressant drugs, which are broad-acting, may not be desirable. Additionally, in order to maintain immunosuppression, immunosuppressant drug therapy is generally a life-long proposition. Unfortunately, the use of broad-acting immunosuppressants are associated with a risk of severe side effects, such as tumors, infections, nephrotoxicity and metabolic disorders. Accordingly, new immunosuppressant therapies would be beneficial.